Agricultural combines are typically equipped with screw conveyors to unload the combines. In these arrangements, a cantilevered screw conveyor is extended from the side of the agricultural combine and suspended with its free cantilevered end in the air, generally at an angle of about 20°. The free cantilevered end is suspended in the air over the side of a vehicle (typically a truck or wagon). This vehicle travels alongside the agricultural combine as it travels through the field.
A large reservoir in the agricultural combine, which is commonly called a grain tank or hopper, is unloaded via this screw conveyor as the combine and vehicle travel through the field. Typically it takes less than 5 minutes to unload 400 bushels of grain in the grain tank into the accompanying vehicle.
One problem with these screw conveyors is their limited capacity. Screws can only operate at limited speed to keep grain damage within reasonable limits. Enlarging a screw conveyor such that it can unload at a higher rate from a larger capacity modern combine requires that the screw conveyor be significantly enlarged. Unfortunately, any significant enlargement would require a much thicker and heavier screw conveyor, which would overbalance the combine do not only to the greater mass of the screw conveyor, but to the larger volume of grain inside the conveyor helix.
It has been proposed to replace the screw conveyor with an endless belt conveyor (or conveyors) in new high capacity agricultural combines. Until now this has not been deemed practical, since an endless belt conveyor would suffer from many of the same problems that the screw conveyor suffers from. Endless belt conveyors typically require multiple idler rollers, heavy frames, and other numerous parts. They take considerable time to assemble, have numerous additional parts and are heavy. For this reason they are not suited to be used as cantilevered conveyors attached to vehicles going over rough terrain at relatively high speed. A screw conveyor, in contrast, typically has only two parts: a cylindrical tube and a rotating helical auger disposed inside the tube.
To provide a practical endless belt conveyor for agricultural combine unloading systems the problems of weight, assembly time and cost must be solved.
As part of the solution to this problem, the applicants have proposed that extrusions, preferably light metal extrusions, be used as the frame of the conveyor. By using extrusions, many additional parts can be eliminated by designing in specific extrusion profiles that can perform the additional functions necessary for a high speed endless belt conveyor.
U.S. Pat. No. 6,012,568 discloses an adjustable conveyor for conveying printed circuit boards in a printed circuit board manufacturing facility. The conveyor uses extrusions best shown in FIG. 5, with multiple cavities that are used to support the printed circuit board, and to guide an endless belt. This conveyor has two separate side rails, each with its own drive mechanism, with two endless belts, on disposal in each of the side rails.